A 5.56 NATO Minimum (GO) and Maximum (NO-GO) Headspace Gauge Set is an essential tool for ensuring the safety and functionality of a rifle chambered in 5.56 NATO. Here’s what the set includes and how it works:

Components
GO Gauge:

Ensures that the chamber is large enough to accept a 5.56 NATO cartridge.
If the bolt closes on the GO gauge, the chamber is at least the minimum specified size.
NO-GO Gauge:

Checks that the chamber does not exceed the maximum acceptable size for safe firing.
If the bolt closes on the NO-GO gauge, the chamber may be unsafe or excessively worn.
Usage
GO Gauge Test:

Ensure the firearm is unloaded and the bolt is disassembled (remove the extractor and ejector).
Insert the GO gauge into the chamber.
Slowly close the bolt.
If the bolt closes fully, the chamber meets the minimum headspace requirement.
NO-GO Gauge Test:

Follow the same steps as above but use the NO-GO gauge.
The bolt should not close fully on the NO-GO gauge. If it does, the chamber exceeds the maximum headspace tolerance, and the firearm may require repair.